1. Field of Invention
The invention relates to keyboards and more particularly to a lighted keyboard with improved characteristics.
2. Description of Related Art
Laptops are widely used by people through out the world due to lightweight and compactness. Typically, a laptop is equipped with a membrane keyboard having a scissors type structure. The scissors type structure is mounted between upper keycaps and a lower rubber plate. However, no backlight is provided by the membrane keyboard. Hence, a user has to operate the laptop in bright environment. This inevitably limits applications of the laptop.
There is a prior art about backlighting for computer keyboard. The keyboard comprises a rubber plate with fastening members for securing scissors shaped structures thereon. No mechanisms are provided to uniformly guide light to undersides of keys. Also, distance from one key to LEDs (light emitting diodes) (i.e., light sources) may be different from distance from another key to the LEDs. That is, traveling distances of the LED light are different. Hence, some proximate keys may be sufficiently illuminated while distal keys may be insufficiently illuminated. In brief, light distribution is not even.
There is another conventional illuminated keyboard commercially available. The keyboard comprises an LED assembly (i.e., light source) on a bottom cabinet, an aluminum plate on the LED assembly, a membrane circuit board on the aluminum plate, and scissors shaped structures and keys on the membrane circuit board. Light emitted by the LED assembly may pass through holes of the aluminum plate and the membrane circuit board toward the undersides of the keys for illumination. However, the provision of the aluminum plate between the LED assembly and the membrane circuit board can increase greatly thickness of the keyboard. That is, the desired feature of a thin keyboard cannot be obtained. Further, its assembly is complicated and time consuming.
OLEDs (organic light emitting diodes) have been widely employed in various lighting and electronic devices including television screens, computer monitors, small, portable system screens such as mobile phones and PDAs, watches, advertising, information and indication. OLEDs can also be used in light sources for general space illumination and in large-area light-emitting elements. In OLED, the emissive electroluminescent layer is a film of organic compounds that emits light when an electric current passes through it. This layer of organic semiconductor material is formed between two electrodes. OLEDs can emit less light per unit area than inorganic solid-state based LEDs similarly designed for use as point-light sources. An OLED display functions without a backlight and so can display deep black levels and can be thinner and lighter than established liquid crystal displays. Similarly, in conditions of low ambient light such as dark rooms, an OLED screen can achieve a higher contrast ratio than either an LCD screen using cold cathode fluorescent lamps or the more recently developed LED backlight. Thus, continuing improvements and applications of OLED backlight are constantly desired.